The present invention relates generally to engine knock sensors.
Most vehicles today are equipped with numerous sensors that are used to regulate the operation of the engine. One such sensor is an engine knock sensor. Typically, an engine knock sensor is mounted on an engine block, e.g., on the intake manifold or a cylinder head, and it produces an output voltage in proportion to the engine vibrations caused by uneven burning of fuel, a.k.a. knock. When knocking occurs, a microprocessor connected to the knock sensor can adjust the engine timing in order to minimize or eliminate the knocking.
Conventional knock sensors include a piezoelectric transducer disposed around a threaded sleeve. A nut is threaded onto the sleeve and then, then the nut is torqued until a spring washer above the transducer is deflected. The spring washer provides a compressive load onto the transducer through a load washer that is installed between the transducer and the spring washer. The sleeve is machined with a hexagonal end opposite the threaded end so that it can be held while the nut is torqued thereon. The need for a nut in combination with the threaded sleeve increases the overall height of the knock sensor. Moreover, the extra manufacturing steps associated with machining the sleeve increase the cost of the sensor dramatically. Also, while the nut is being torqued onto the sleeve there is a chance that debris from one of the internal components can be created. This debris can short the sensor during the life thereof.
The present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
A threadless knock sensor includes a sleeve having a transducer disposed therearound. A load washer is disposed around the sleeve adjacent to the transducer. Moreover, a frusto-conical disk spring is disposed around the sleeve adjacent to the load washer. The threadless knock sensor also includes a threadless means for compressing the disk spring against the load washer.
In one aspect of the knock sensor the threadless means includes a flared end formed by the sleeve above the load washer. The disk spring is installed in compression between the flared end of the sleeve and the load washer. In this aspect of the knock sensor, the disk spring defines an inner periphery formed with at least one slit therethrough. In order to facilitate installation of the disk spring over the flared end of the sleeve, the slit is angled with respect to vertical.
In another aspect of the knock sensor, the threadless means includes a spring retention collar press fitted around the sleeve above the load washer. The disk spring is installed in compression between the spring retention collar and the load washer.
In a preferred embodiment, the knock sensor includes a lower terminal that is disposed around the sleeve beneath the transducer. Moreover, an upper terminal is disposed around the sleeve above the transducer. Preferably, a lower insulator is disposed around the sleeve beneath the lower terminal and an upper insulator is disposed around the sleeve above the upper terminal. Also, in a preferred embodiment, a plastic housing surrounds the sleeve, the transducer, the terminals, the insulators, and the disk spring. Preferably, the disk spring is formed with holes to allow molten plastic to flow therethrough.
In another aspect of the present invention, an engine control system includes a microprocessor. An ignition system is electrically connected to the microprocessor. Moreover, a threadless knock sensor is electrically connected to the microprocessor.
In yet another aspect of the present invention, a method for making an engine knock sensor includes providing a sleeve that has a flared end. The flared end defines a first spring retention face. A transducer is disposed on the sleeve and a load washer is disposed on the sleeve above the transducer. The load washer forms a second spring retention face. Then, a disk spring is disposed on the sleeve above the load washer such that it contacts the second spring retention face. The disk spring is compressed until it engages the first spring retention face.
In still another aspect of the present invention, a method for making an engine knock sensor includes providing a sleeve that forms a collar stop face. A transducer is disposed on the sleeve and a load washer is disposed on the sleeve above the transducer. Moreover, a disk spring is disposed on the sleeve above the load washer. Then, a spring retention collar is pressed on the sleeve above the disk spring until the spring retention collar engages the collar stop face and the disk spring is compressed.
In yet still another aspect of the present invention, an engine knock sensor includes a sleeve and a transducer that circumscribes the sleeve. The knock sensor further includes an upper threadless spring retention element and a lower spring retention element. In this aspect, a spring is held in compression between the retention elements to exert a load on the transducer.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: